WO2018043500A1

WO2018043500A1 - Optical filter

Info

Publication number: WO2018043500A1
Application number: PCT/JP2017/030996
Authority: WO
Inventors: 大西　学; 秀史齊藤; 祐貴藤井; 佑一加茂; 正垣　達也
Original assignee: 株式会社大真空
Priority date: 2016-08-31
Filing date: 2017-08-29
Publication date: 2018-03-08
Also published as: JPWO2018043500A1; TW201819963A; CN109983374A; US20190250316A1

Abstract

[Problem] To provide an optical filter that can sufficiently suppress transmission of red components. [Solution] An optical filter 10 has a second filter 30 formed on one surface 20A of a first filter 20 and has a third filter 40 formed on the other surface 20B of the first filter 20. Along with having blocking characteristics in a first band A1 provided from the long wavelength side of the visible light region to the near-infrared light region and a third band A3 provided on the longer wavelength side than the first band, the optical filter has transmission characteristics in a second band A2 provided between the first band A1 and the third band A3. In the first band A1, the bandwidth for the blocked band with transmittance of 5% or less is set to at least 100 nm.

Description

Optical filter

The present invention relates to an optical filter provided in an imaging device.

As an optical filter provided in an imaging device, an optical filter having transmission characteristics in two wavelength bands of a visible light region and a near infrared light region is known. According to such an optical filter, it is possible to perform photographing not only in daylight when natural light enters but also under night vision such as at night.

As an optical filter as described above, for example, Patent Document 1 discloses an infrared absorption substrate (infrared absorber) having a characteristic of absorbing light in the near infrared region, and a dielectric multilayer film formed on the infrared absorption substrate. An optical filter is described. In addition, as an infrared absorbing substrate, it is described that an infrared absorbing resin in which a transparent resin contains a compound that absorbs infrared rays is used.

Japanese Patent No. 5888953

The optical filter described in Patent Literature 1 includes a first band (light blocking band Za) provided in the near infrared light region and a third band (light blocking band) provided on the longer wavelength side than the first band. Zc) has a cutoff characteristic and also has a transmission characteristic in a second band (light transmission band Zb) provided between the first band and the third band. However, in the optical filter described in Patent Document 1, it cannot be said that the cutoff characteristic of the first band is sufficiently ensured in the near-infrared light region. There is a possibility that the color reproducibility of an image picked up by the device is lowered.

The present invention has been made in view of such points, and an object thereof is to provide an optical filter capable of sufficiently suppressing transmission of a red component.

In the present invention, means for solving the above-described problems are configured as follows. That is, the present invention is an optical filter having transmission characteristics in two wavelength bands of a visible light region and a near-infrared light region, and a dielectric multilayer film is formed on one surface of a first filter made of an infrared absorber. A second filter is formed, a third filter made of a dielectric multilayer film is formed on the other surface of the first filter, and the first filter is provided from the long wavelength side of the visible light region to the near infrared light region. It has a cutoff characteristic in the band and the third band provided on the longer wavelength side than the first band, and has a transmission characteristic in the second band provided between the first band and the third band. In the first band, the bandwidth of the cutoff band where the transmittance is 5% or less is set to at least 100 nm.

According to the above configuration, in the first band of the optical filter, since the bandwidth of the cutoff band where the transmittance is 5% or less is set to at least 100 nm, a wider bandwidth of the cutoff band is ensured than in the past. Therefore, it is possible to sufficiently secure the cutoff characteristic of the first band. Thereby, the transmission of the red component can be sufficiently suppressed, and the occurrence of color mixing due to the transmission of the red component can be suppressed. As a result, it is possible to suppress a decrease in color reproducibility of an image captured by the imaging device.

In the optical filter configured as described above, in the first filter, the wavelength at which the transmittance is 50% in the visible light region is a wavelength in the range of 640 nm to 660 nm, and the absorption maximum is in the range of 650 nm to 800 nm. In the second filter, the wavelength at which the transmittance is 50% is a wavelength in the range of 685 nm to 710 nm, and the cutoff band at which the transmittance is 5% or less is near infrared light. The region may be provided over a range of at least 100 nm. The second filter may be configured by combining a plurality of filters.

According to the above configuration, by using the infrared absorber having the above characteristics as the first filter, it is possible to reduce the incident angle dependency in the visible light region, and in the image captured by the imaging device, Generation of flare can also be suppressed.

In the optical filter having the above configuration, the wavelength at which the transmittance of the second filter is 50% may be longer than the wavelength at which the transmittance is 50% in the visible light region of the first filter. .

According to the above configuration, the half-value wavelength of the second filter (the wavelength at which the transmittance is 50%) is on the longer wavelength side than the half-value wavelength in the visible light region of the first filter. Due to the absorption, the amount of light reflected by the second filter is suppressed. Thereby, generation | occurrence | production of the ghost resulting from reflection of the light by a 2nd filter can be suppressed.

In the optical filter configured as described above, the first band may be formed by the first filter and the second filter, and the third band may be formed by the third filter. Alternatively, the cutoff characteristic on the short wavelength side of the first band is formed by the first filter, and the transmission characteristic on the short wavelength side of the second band is formed by the second filter, and the length of the second band is The transmission characteristic on the wavelength side may be formed by the third filter.

According to the above configuration, in the second band, it is possible to easily change the bandwidth of the transmission band where the transmittance is 50% or more, and flexibly meet various requirements for the filter characteristics in the near-infrared light region of the optical filter. It can correspond to. Note that the bandwidth of the transmission band where the transmittance of the second band is 50% can be set to 35 nm to 200 nm. Further, it is possible to set the transmission band in which the transmittance of the second band is 50% in the range of 800 nm to 1000 nm.

In the optical filter having the above-described configuration, the first filter may have a configuration in which an infrared absorbing dye is applied to a transparent substrate, and the third filter may be configured by an antireflection film. According to this configuration, by adjusting the type, concentration, thickness, and the like of the infrared absorbing dye, desired infrared absorption characteristics can be easily obtained as compared with the case where the infrared absorbing resin substrate is used.

In the optical filter configured as described above, the first band may be formed by the first filter and the second filter, and the third band may be formed by the second filter. Alternatively, the cutoff characteristic on the short wavelength side of the first band is formed only by the first filter or by the first filter and the second filter, and the transmission characteristic on the short wavelength side of the second band, and The transmission characteristics on the long wavelength side of the second band may be formed by the second filter. According to these configurations, the second filter capable of forming the transmission characteristics of the second band with a single filter can be formed on the surface opposite to the surface on which the infrared absorbing dye is formed. Damage to the infrared absorbing dye (particularly damage due to heat) can be suppressed.

In the optical filter configured as described above, the bandwidth of the wavelength at which the transmittance of the first band is 50%, the bandwidth of the wavelength at which the transmittance of the first filter is 50%, and the transmittance of the second filter are It may be larger than the bandwidth of the wavelength that is 50%.

According to the above configuration, the first and second filters can set the transmission band (second band) in a desired range in the near-infrared light region, and reduce the incident angle dependency in the visible light region. Therefore, it is possible to suppress the occurrence of ghost and flare in the image captured by the imaging device.

In the optical filter having the above configuration, the second filter has a configuration in which a plurality of high refractive index films and a plurality of low refractive index films having a refractive index smaller than that of the high refractive index film are alternately stacked. In the second filter, the average value of the optical film thickness of the low refractive index film is smaller than the average value of the optical film thickness of the high refractive index film, and the average optical film thickness of the low refractive index film The film thickness ratio between the value and the average optical film thickness of the high refractive index film may be 0.50 to 0.85.

According to the above configuration, the bandwidth of the cutoff band having the cutoff characteristic of the second filter can be narrowed, and the transmission band (second band) is in a desired range in the near-infrared light region separated from the visible light region. Can be set.

According to the optical filter of the present invention, in the first band, the bandwidth of the cutoff band where the transmittance is 5% or less is set to at least 100 nm. Therefore, it is possible to sufficiently secure the cutoff characteristic of the first band. Thereby, the transmission of the red component can be sufficiently suppressed, and the occurrence of color mixing due to the transmission of the red component can be suppressed. As a result, it is possible to suppress a decrease in color reproducibility of an image captured by the imaging device.

It is a figure which shows schematic structure of the imaging device using the optical filter which concerns on this invention. It is a figure which shows typically schematic structure of the optical filter which concerns on this invention. It is a figure which shows an example of the filter characteristic of the optical filter of FIG. It is a figure which shows an example of the filter characteristic of the 1st filter of the optical filter of FIG. It is a table | surface which shows an example of a structure of each layer of the 2nd filter of the optical filter of FIG. It is a figure which shows an example of the filter characteristic of the 2nd filter of FIG. It is a table | surface which shows an example of a structure of each layer of the 3rd filter of the optical filter of FIG. It is a figure which shows an example of the filter characteristic of the 3rd filter of FIG. In the optical filter of FIG. 2, it is a figure which shows a part of each filter characteristic when the incident angles of light are 0 degree, 10 degrees, 20 degrees, and 30 degrees. It is a figure which shows typically schematic structure of the optical filter which concerns on other embodiment of this invention. It is a figure which shows an example of the filter characteristic of the optical filter of FIG. It is a figure which shows an example of the filter characteristic of the 1st filter of the optical filter of FIG. It is a figure which shows an example of the filter characteristic of the 2nd filter of the optical filter of FIG. It is a table | surface which shows an example of a structure of each layer of the 3rd filter of the optical filter of FIG. It is a figure which shows an example of the filter characteristic of the 3rd filter of FIG.

Hereinafter, an embodiment (first embodiment) of an optical filter according to the present invention will be described with reference to the drawings. The optical filter according to the present embodiment is an optical filter provided in an imaging device, and has transmission characteristics in two wavelength bands of a visible light region and a near infrared light region. The wavelength band having the transmission characteristic in the visible light region and the wavelength band having the transmission characteristic in the near infrared light region are provided apart from each other. In the present embodiment, the visible light region refers to a region where the wavelength of light is about 400 nm to about 700 nm, and the near infrared light region refers to a region where the wavelength of light is about 700 nm to about 1100 nm.

FIG. 1 is a diagram illustrating a schematic configuration of an imaging device using the optical filter 10. FIG. 2 is a diagram schematically showing a schematic configuration of the optical filter 10. FIG. 3 is a diagram illustrating an example of the filter characteristics of the optical filter 10.

As shown in FIG. 1, in the imaging device, the optical filter 10 transmits light of two wavelengths in the visible light region and the near infrared light region with respect to the light collected by the lens 80, It is an optical filter that makes light incident on an image sensor 90 such as a CMOS. FIG. 1 illustrates a case where light is incident on the lens 80 from a vertical direction and a case where light is incident on the lens 80 from an oblique direction with an incident angle α.

As shown in FIG. 2, the optical filter 10 includes a first filter 20 made of an infrared absorber, a second filter 30 made of a dielectric multilayer film coated on one surface of the first filter 20, and a first filter. 20 and a third filter 40 made of a dielectric multilayer film coated on the other surface. The optical filter 10 exhibits filter characteristics (transmittance waveform) as shown in FIG. Hereinafter, each configuration of the optical filter 10 will be described.

-First filter-
The 1st filter 20 is comprised by the infrared rays absorption board | substrate (infrared absorber) which has the characteristic which absorbs the light of a near-infrared-light area | region. In the present embodiment, as the infrared absorber constituting the first filter 20, an infrared absorbing resin in which a transparent resin contains a compound (pigment) that absorbs infrared rays is used. As a transparent resin and a pigment | dye, it is possible to use a well-known substance as shown, for example in patent 5888953.

As shown in FIG. 4, the first filter 20 has an absorption maximum near the boundary between the visible light region and the near-infrared light region, and the transmittance of the first filter 20 is minimized. FIG. 4 shows the filter characteristics of the first filter 20 when the light incident angle α (see FIG. 1) is 0 ° (in the case of vertical incidence).

Specifically, the first filter 20 has transmission characteristics in substantially the entire visible light region (400 nm to 700 nm), and gently transmits on the long wavelength side (longer wavelength side than 600 nm) of the visible light region. It has a transmission characteristic with a decreasing rate. In the visible light region, the range in which the transmittance of the first filter 20 is 50% or more is a wavelength band from the short wavelength end (400 nm) of the visible light region to approximately 650 nm. The range where the transmittance of the first filter 20 is 80% or more is the wavelength band from the short wavelength end (400 nm) of the visible light region to approximately 615 nm. The range in which the transmittance of the first filter 20 is 90% or more is a wavelength band of approximately 440 nm to approximately 590 nm. The range in which the transmittance of the first filter 20 is 95% or more is a wavelength band of about 458 nm to about 570 nm.

The first filter 20 has a transmission characteristic in substantially the entire region of the near infrared light region (700 nm to 1100 nm), and the transmittance on the short wavelength side (shorter wavelength side than 750 nm) of the near infrared light region. Has increased transmission characteristics. In the near infrared light region, the range in which the transmittance of the first filter 20 is 50% or more is a wavelength band from approximately 750 nm to the long wavelength end (1100 nm) of the near infrared light region. The range in which the transmittance of the first filter 20 is 80% or more is the wavelength band from approximately 760 nm to the long wavelength end (1100 nm) in the near infrared light region. The range in which the transmittance of the first filter 20 is 90% or more is the wavelength band from approximately 770 nm to the long wavelength end (1100 nm) in the near infrared light region. The range in which the transmittance of the first filter 20 is 95% or more is the wavelength band from approximately 776 nm to the long wavelength end (1100 nm) in the near infrared light region. On the short wavelength side in the near infrared light region, the change rate (increase rate) of the transmittance of the first filter 20 is larger than the change rate (decrease rate) on the long wavelength side in the visible light region.

On the other hand, the absorption characteristics of the first filter 20 in the vicinity of the boundary between the visible light region and the near infrared light region are as follows. The range in which the transmittance of the first filter 20 is 20% or less is a wavelength band of approximately 680 nm to approximately 740 nm. The range in which the transmittance of the first filter 20 is 10% or less is a wavelength band of about 686 nm to about 728 nm. The range in which the transmittance of the first filter 20 is 5% or less is a wavelength band of approximately 690 nm to approximately 716 nm. The transmittance of the first filter 20 is the minimum value (approximately 1.9%) at a wavelength of approximately 704 nm (absorption maximum). In the present embodiment, the absorption maximum of the first filter 20 exists at a wavelength of approximately 704 nm. However, the absorption maximum of the first filter 20 is within a range of 650 nm to 800 nm. For example, as another example of the first filter 20, as shown by a broken line in FIG. 4, it may have an absorption maximum at a wavelength of about 760 nm.

-Second filter-
As shown in FIG. 2, the second filter 30 is configured by a dielectric multilayer film formed on one surface 20 A of the first filter 20. Specifically, as shown in FIG. 5, the second filter 30, and TiO ₂ is a high-refractive-index film 30H, has a structure in which the SiO ₂ which is a low refractive index film 30L are stacked alternately . The high refractive index film 30 H and the low refractive index film 30 L are each formed in 15 layers, and a total of 30 layers are formed. The odd-numbered layers counted from the first filter 20 side are high-refractive-index films 30H, and the even-numbered layers are low-refractive-index films 30L. The first layer (lowermost layer) closest to the first filter 20 is the high refractive index film 30H, and the 30th layer (uppermost layer) closest to the atmosphere is the low refractive index film 30L. The order in which the high refractive index film 30H and the low refractive index film 30L are stacked is not limited to this example. The odd-numbered layers counted from the first filter 20 side are the low-refractive index films 30L, and the even-numbered layers are high. The refractive index film 30H may be used. Further, the number of layers of the high refractive index film 30H and the low refractive index film 30L may be different by one. For example, the number of layers of the low refractive index film 30L is set to the high refractive index similarly to the third filter 40 described later. One more than the number of layers of the film 30H is also possible.

In the present embodiment, the high refractive index film 30H is made of TiO ₂ , but is not limited thereto, and may be a material such as ZrO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , for example. That is, the material of the high refractive index film 30H is preferably a material having a refractive index larger than 2.0. Further, the low refractive index film 30L is not limited to SiO ₂ but may be a material such as MgF ₂ . That is, the material of the low refractive index film 30L is preferably a material having a refractive index smaller than that of the high refractive index film 30H, and more preferably a material having a refractive index smaller than 1.5.

Each layer (the low refractive index film 30L and the high refractive index film 30H) of the second filter 30 is alternately vacuum deposited by a known vacuum deposition apparatus. The vapor deposition film thickness is designed based on the optical film thickness Nd which is the product of the refractive index N and the physical film thickness d, and the optical film thickness of the second filter 30 is designed as shown in FIG. 5, for example. ing. Note that there is a relationship [Nd = λ / 4] between the optical film thickness Nd and the center wavelength λ. The center wavelength (720 nm) in FIG. 5 is the center wavelength when designing the film thickness.

As shown in FIG. 5, the second filter 30 includes a total of 30 layers of a high refractive index film 30H and a low refractive index film 30L, and the total film thickness (physical film thickness) at that time is about 3.1 μm. It has become. The number of layers of the second filter 30 is preferably 20 to 60 layers, and the total film thickness at that time is preferably 2.0 μm to 6.0 μm.

The optical film thickness of the low refractive index film 30L of the second filter 30 is 0.10 to 2.58, and the average value of the optical film thickness is 0.93. The optical film thickness of the high refractive index film 30H of the second filter 30 is 0.18 to 1.78, and the average value of the optical film thickness is 1.21. Thus, in the second filter 30, the average value of the optical film thickness of the low refractive index film 30L is smaller than the average value of the optical film thickness of the high refractive index film 30H, and the optical value of the low refractive index film 30L. Thickness ratio between the average value of the film thickness and the average value of the optical film thickness of the high refractive index film 30H [average value of the optical film thickness of the low refractive index film 30L / average value of the optical film thickness of the high refractive index film 30H ] Is 0.77. The film thickness ratio between the average value of the optical film thickness of the low refractive index film 30L and the average value of the optical film thickness of the high refractive index film 30H is preferably 0.50 to 0.85.

As shown in FIG. 6, the second filter 30 has a transmission characteristic in substantially the entire visible light region (400 nm to 700 nm) and a transmission characteristic in a part of the near infrared light region (700 nm to 1100 nm). FIG. 6 shows the filter characteristics of the second filter 30 with a solid line when the incident angle α of light (see FIG. 1) is 0 ° (in the case of vertical incidence). A broken line (thin line) in FIG. 6 indicates a filter characteristic obtained by combining the filter characteristic of the first filter 20 (see FIG. 4) and the filter characteristic of the second filter 30 described above.

Specifically, the second filter 30 has a transmission characteristic in substantially the entire visible light region (400 nm to 700 nm), and rapidly transmits on the long wavelength side (longer wavelength side than 680 nm) of the visible light region. It has a transmission characteristic with a decreasing rate. In the visible light region, the range where the transmittance of the second filter 30 is 50% or more is the wavelength band from the short wavelength end (400 nm) of the visible light region to approximately 694 nm. The range where the transmittance of the second filter 30 is 80% or more is the wavelength band from the short wavelength end (400 nm) of the visible light region to about 690 nm. The range in which the transmittance of the second filter 30 is 90% or more is a wavelength band of approximately 408 nm to approximately 688 nm. A range where the transmittance of the second filter 30 is 95% or more is a wavelength band of about 410 nm to about 686 nm.

The second filter 30 has transmission characteristics in a part of the near infrared light region (700 nm to 1100 nm). The wavelength band having the transmission characteristics in the near-infrared light region of the second filter 30 is provided apart from the wavelength band having the transmission characteristics in the visible light region. Specifically, the second filter 30 has a transmission characteristic in a part of the wavelength band of 800 nm to 950 nm, and the transmittance rapidly increases on the longer wavelength side than 800 nm in the near infrared light region. It has a transmission characteristic in which the transmittance sharply decreases on the shorter wavelength side than 950 nm. In the near-infrared light region, the range in which the transmittance of the second filter 30 is 50% or more is a wavelength band of approximately 830 nm to approximately 916 nm. The range in which the transmittance of the second filter 30 is 80% or more is a wavelength band of about 836 nm to about 908 nm. The range in which the transmittance of the second filter 30 is 90% or more is a wavelength band of approximately 838 nm to approximately 904 nm. The range in which the transmittance of the second filter 30 is 95% or more is a wavelength band of approximately 840 nm to approximately 902 nm.

On the other hand, the cutoff characteristic of the second filter 30 in the vicinity of the boundary between the visible light region and the near-infrared light region is as follows. The range in which the transmittance of the second filter 30 is 20% or less is a wavelength band of about 700 nm to about 824 nm. The range in which the transmittance of the second filter 30 is 10% or less is a wavelength band of about 706 nm to about 818 nm. The range where the transmittance of the second filter 30 is 5% or less is the wavelength band of approximately 712 nm to approximately 812 nm.

-Third filter-
As shown in FIG. 2, the third filter 40 is composed of a dielectric multilayer film formed on the other surface 20 B of the first filter 20. Specifically, as shown in FIG. 7, the third filter 40, the TiO ₂ is a high-refractive-index film 40H, has a structure in which the SiO ₂ which is a low refractive index film 40L are stacked alternately . The high refractive index film 40H is formed of 12 layers, and the low refractive index film 40L is formed of 13 layers, for a total of 25 layers. The odd-numbered layers counted from the first filter 20 side are the low-refractive index films 40L, and the even-numbered layers are the high-refractive index films 40H. The first layer (lowermost layer) on the first filter 20 side is the low refractive index film 40L, and the 25th layer (uppermost layer) on the most atmospheric side is also the low refractive index film 40L. The order in which the high refractive index film 40H and the low refractive index film 40L are stacked is not limited to this example. The odd-numbered layers counted from the first filter 20 side are the high-refractive index films 40H, and the even-numbered layers are low. The refractive index film 40L may be used. For example, similarly to the second filter 30 described above, the number of layers of the high refractive index film 40H and the low refractive index film 40L may be the same.

In the present embodiment, the high refractive index film 40H is made of TiO ₂ , but is not limited thereto, and may be a material such as ZrO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , for example. That is, as the material for the high refractive index film 40H, a material having a refractive index larger than 2.0 is preferable. Further, the low refractive index film 40L is not limited to SiO ₂ but may be a material such as MgF ₂ . That is, the material of the low refractive index film 40L is preferably a material having a refractive index smaller than that of the high refractive index film 40H, and more preferably a material having a refractive index smaller than 1.5.

Each layer of the third filter 40 (low refractive index film 40L and high refractive index film 40H) is alternately vacuum-deposited by a known vacuum deposition apparatus. The vapor deposition film thickness is designed based on the optical film thickness that is the product of the refractive index and the physical film thickness, and the optical film thickness of the third filter 40 is designed, for example, as shown in FIG. The center wavelength (720 nm) in FIG. 7 is the center wavelength when designing the film thickness.

As shown in FIG. 7, in the third filter 40, a total of 25 layers of a high refractive index film 40H and a low refractive index film 40L are laminated, and the total film thickness (physical film thickness) at that time is about 3.0 μm. It has become. The number of layers of the second filter 30 is preferably 20 to 60 layers, and the total film thickness at that time is preferably 2.4 μm to 7.2 μm.

As shown in FIG. 8, the third filter 40 has transmission characteristics in a substantially entire visible light region (400 nm to 700 nm) and a short wavelength side region of the near infrared light region (700 nm to 1100 nm). FIG. 8 shows the filter characteristics of the third filter 40 when the light incident angle α (see FIG. 1) is 0 ° (in the case of vertical incidence).

Specifically, the third filter 40 has transmission characteristics from the short wavelength end (400 nm) of the visible light region to the near infrared light region, and in the near infrared light region (shorter wavelength side than 900 nm). And has a transmission characteristic in which the transmittance decreases rapidly. In substantially the entire visible light region, the transmittance of the third filter 40 is 95% or more. Further, in the near infrared light region, the third filter 40 has a transmittance of 95% or more from the short wavelength end (700 nm) of the near infrared light region to the shorter wavelength side than 900 nm. In this case, the transmittance of the third filter 40 is 95% at a wavelength of approximately 862 nm. Further, the transmittance of the third filter 40 is 90% at a wavelength of about 866 nm, the transmittance of the third filter 40 is 80% at a wavelength of about 870 nm, and the transmission of the third filter 40 is at a wavelength of about 876 nm. The rate is 50%.

On the other hand, the cutoff characteristic of the third filter 40 in the near-infrared light region is as follows. The range in which the transmittance of the third filter 40 is 20% or less is a wavelength band from approximately 886 nm to the long wavelength end (1100 nm) in the near infrared light region. The range in which the transmittance of the third filter 40 is 10% or less is a wavelength band from approximately 892 nm to the long wavelength end (1100 nm) of the near infrared light region. The range in which the transmittance of the third filter 40 is 5% or less is a wavelength band from approximately 900 nm to the long wavelength end (1100 nm) in the near infrared light region.

-Optical filter characteristics-
The filter characteristics of the first to

third filters

20, 30, and 40 of the present embodiment are as shown in FIGS. 4, 6, and 8, respectively. The filter characteristics of the entire optical filter 10 are obtained by integrating the filter characteristics of the first filter 20, the filter characteristics of the second filter 30, and the filter characteristics of the third filter 40 (see FIG. 3). That is, the transmittance waveform of the first filter 20 (see FIG. 4), the transmittance waveform of the second filter 30 (see FIG. 6), and the transmittance waveform of the third filter 40 (see FIG. 8) overlap. A transmittance waveform of the optical filter 10 shown in FIG. 3 is obtained. That is, according to the optical filter 10 of the present embodiment, as shown in FIG. 3, filter characteristics having transmission characteristics in two wavelength bands of the visible light region and the near infrared light region can be obtained. The wavelength band having transmission characteristics in the near-infrared light region of the optical filter 10 is provided apart from the wavelength band having transmission properties in the visible light region.

Specifically, as shown in FIG. 3, the optical filter 10 has transmission characteristics in substantially the entire visible light region (400 nm to 700 nm), and has a longer wavelength side (wavelength longer than 600 nm) in the visible light region. Side), the transmittance gradually decreases. Such characteristics of the optical filter 10 in the visible light region are mainly obtained by the first filter 20. The waveform in which the transmittance of the optical filter 10 decreases on the long wavelength side (longer wavelength side than 600 nm) in the visible light region is substantially similar to the waveform in which the transmittance of the first filter 20 decreases. That is, in the region on the long wavelength side of the visible light region, the transmittance of the second filter 30 and the third filter 40 is approximately 100% (95% or more). The filter characteristics of the filter 20 are reflected almost as they are.

More specifically, the range in which the transmittance of the optical filter 10 is 50% or more in the visible light region is the wavelength band from the short wavelength end (400 nm) of the visible light region to approximately 646 nm. The range in which the transmittance of the optical filter 10 is 80% or more is a wavelength band of about 420 nm to about 610 nm. A range where the transmittance of the optical filter 10 is 90% or more is a wavelength band of about 450 nm to about 580 nm. A range where the transmittance of the optical filter 10 is 95% or more is a wavelength band of about 470 nm to about 540 nm.

Further, as shown in FIG. 3, the optical filter 10 has transmission characteristics in a part of the near-infrared light region. That is, the optical filter 10 is cut off in the first band A1 provided from the long wavelength side of the visible light region to the near infrared light region and the third band A3 provided on the longer wavelength side than the first band A1. In addition to having a characteristic, the second band A2 provided between the first band A1 and the third band A3 has a transmission characteristic.

The first band A1 is provided from a longer wavelength side than 640 nm to a longer wavelength side than 800 nm, and a cutoff band having a transmittance of 5% or less is provided in the first band A1. The third band A3 is provided from the shorter wavelength side than 900 nm to the long wavelength end (1100 nm) in the near-infrared light region, and the third band A3 has a cutoff band in which the transmittance is 5% or less. Is provided. The transmission band of the second band A2 is formed by the cutoff band of the first band A1 and the cutoff band of the third band A3. In the second band A2, the transmittance of the optical filter 10 is 50% at a wavelength longer than 800 nm (approximately 830 nm) and a wavelength shorter than 900 nm (approximately 876 nm).

Specifically, as shown in FIG. 3, the wavelength band in which the transmittance of the first band A1 is 50% is a wavelength band of about 646 nm to about 830 nm. The wavelength band in which the transmittance of the second band A2 is 50% is a wavelength band of approximately 830 nm to approximately 876 nm. The wavelength band in which the transmittance of the third band A3 is 50% is a wavelength band from approximately 876 nm to the long wavelength end (1100 nm) of the near infrared light region.

The cutoff characteristics in the first band A1 of the optical filter 10 are as follows. The range in which the transmittance of the optical filter 10 is 20% or less is a wavelength band of approximately 680 nm to approximately 824 nm. The range in which the transmittance of the optical filter 10 is 10% or less is a wavelength band of about 686 nm to about 818 nm. The range in which the transmittance of the optical filter 10 is 5% or less is a wavelength band of about 690 nm to about 812 nm. As described above, the optical filter 10 has a characteristic that in the first band A1, the transmittance rapidly increases on the longer wavelength side than 800 nm in the near-infrared light region.

Further, the cutoff characteristic in the third band A3 of the optical filter 10 is as follows. The range in which the transmittance of the optical filter 10 is 20% or less is a wavelength band from approximately 884 nm to the long wavelength end (1100 nm) of the near infrared light region. The range in which the transmittance of the optical filter 10 is 10% or less is a wavelength band from approximately 892 nm to the long wavelength end (1100 nm) in the near infrared light region. The range in which the transmittance of the optical filter 10 is 5% or less is a wavelength band from approximately 900 nm to the long wavelength end (1100 nm) of the near infrared light region. As described above, the optical filter 10 has a characteristic that in the third band A3, the transmittance sharply decreases on the shorter wavelength side than 900 nm in the near infrared light region.

On the other hand, the transmission characteristics of the optical filter 10 in the second band A2 are as follows. The range in which the transmittance of the optical filter 10 is 50% or more is a wavelength band of approximately 830 nm to approximately 876 nm. The range in which the transmittance of the optical filter 10 is 80% or more is a wavelength band of about 836 nm to about 870 nm. A range where the transmittance of the optical filter 10 is 90% or more is a wavelength band of about 840 nm to about 866 nm. The range in which the transmittance of the optical filter 10 is 95% or more is a wavelength band of approximately 842 nm to approximately 864 nm. Thus, in the second band A2, the optical filter 10 has a characteristic that the transmittance rapidly increases on the longer wavelength side than 800 nm in the near infrared light region, and from 900 nm in the near infrared light region. Also has a characteristic that the transmittance decreases rapidly on the short wavelength side.

In the present embodiment, the cutoff characteristic on the short wavelength side of the first band A1 of the optical filter 10 is formed by the first filter 20. Further, the cutoff characteristic on the long wavelength side of the first band A1 of the optical filter 10 and the transmission characteristic on the short wavelength side of the second band A2 are formed by the second filter 30. In addition, the transmission characteristics on the long wavelength side of the second band A2 of the optical filter 10 and the cutoff characteristics on the short wavelength side of the third band A3 are formed by the third filter 40. In the first band A1 of the optical filter 10, the bandwidth of the cutoff band where the transmittance is 5% or less is at least 100 nm. This point will be described below.

As shown in FIG. 3, in the first band A1, in the near-infrared light region, the optical filter 10 has a wavelength band from the short wavelength end (700 nm) of the near-infrared light region to the longer wavelength side than 800 nm. A cut-off band in which the transmittance is 5% or less is provided. More specifically, the cutoff band of the first band A1 is continuously provided not only in the near-infrared light region but also on the long wavelength side of the visible light region, and specifically, approximately 690 nm to approximately 812 nm. It is provided in the range.

The cut-off band of the first band A1 of the optical filter 10 is formed by the first filter 20 and the second filter 30. Specifically, in the visible light region, in the wavelength band from the long wavelength side (approximately 690 nm) of the visible light region to the long wavelength end (700 nm) of the visible light region, the cutoff band of the first band A1 is the first The filter 20 roughly follows the filter characteristics of the filter 20. That is, in the wavelength band from the long wavelength side (approximately 690 nm) of the visible light region to the long wavelength end (700 nm) of the visible light region, the transmittance of the first filter 20 is approximately 0% (5% or less). Therefore, the filter characteristic of the optical filter 10 reflects the filter characteristic of the first filter 20 almost as it is.

In the near infrared light region, in the wavelength band from the short wavelength end (700 nm) of the near infrared light region to the short wavelength side (approximately 712 nm) of the near infrared light region, the cutoff band of the first band A1 is The filter characteristics of the first filter 20 and the filter characteristics of the second filter 30 are combined. On the other hand, in the wavelength band from the short wavelength side (approximately 712 nm) in the near-infrared light region to the longer wavelength side (approximately 812 nm) than 800 nm, the cutoff band of the first band A1 is the filter characteristic of the second filter 30. It has been imitated. That is, in the wavelength band from the short wavelength side (approximately 712 nm) in the near infrared light region to the longer wavelength side (approximately 812 nm) than 800 nm, the transmittance of the second filter 30 is approximately 0% (5% or less). Therefore, the filter characteristic of the optical filter 10 reflects the filter characteristic of the second filter 30 substantially as it is.

Thus, the cut-off band of the first band A1 of the optical filter 10 is formed by the first filter 20 and the second filter 30. In the first band A1 of the optical filter 10, the bandwidth of the cut-off band where the transmittance is 5% or less in the near infrared light region is set to at least 100 nm, and in this example, is approximately 112 nm. . Considering not only the near-infrared light region but also the long wavelength side of the visible light region, the bandwidth of the cutoff band in which the transmittance of the first band A1 of the optical filter 10 is 5% or less is in the visible light region. From the long wavelength side to the near infrared light region, it is approximately 122 nm.

Next, the optical filter 10 has a filter characteristic in which the transmittance rapidly increases near the boundary between the first band A1 and the second band A2 on the longer wavelength side than 800 nm in the near-infrared light region. In the range of about 812 nm to about 842 nm, the transmittance of the optical filter 10 increases from 5% to 95%. The cut-off characteristic on the long wavelength side of the first band A1 and the transmission characteristic on the short wavelength side of the second band A2 of the optical filter 10 substantially follow the filter characteristic of the second filter 30. That is, the transmittance of the first filter 20 and the third filter 40 is approximately 100% (95% or more) on the longer wavelength side (approximately 812 nm to approximately 842 nm) than 800 nm in the near infrared light region. The filter characteristics of the optical filter 10 reflect the filter characteristics of the second filter 30 almost as they are. As described above, the second filter 30 forms the cutoff characteristic on the long wavelength side of the first band A1 of the optical filter 10 and the transmission characteristic on the short wavelength side of the second band A2.

Next, in the second band A2, the transmittance of the optical filter 10 in the wavelength band from the longer wavelength side than 800 nm to the shorter wavelength side than 900 nm, specifically, in the wavelength band of about 842 nm to about 864 nm. A transmission band of 95% or more is provided. The transmission band of the second band A2 of the optical filter 10 is substantially similar to the filter characteristics of the second filter 30 and the third filter 40. That is, in the wavelength band of approximately 842 nm to approximately 864 nm, the transmittance of the first filter 20 and the third filter 40 is approximately 100% (95% or more), so that the filter characteristic of the optical filter 10 is the second filter. The 30 filter characteristics are reflected as they are. Thus, the transmission band of the second band A2 of the optical filter 10 is formed by the second filter 30. In the second band A2 of the optical filter 10, the bandwidth of the transmission band where the transmittance is 95% or more is approximately 22 nm in this example. In the second band A2 of the optical filter 10, the bandwidth of the transmission band where the transmittance is 50% or more is approximately 46 nm in this example.

Next, the optical filter 10 has a filter characteristic in which the transmittance rapidly decreases near the boundary between the second band A2 and the third band A3 on the shorter wavelength side than 900 nm in the near-infrared light region. In the range from about 864 nm to about 900 nm, the transmittance of the optical filter 10 decreases from 95% to 5%. The transmission characteristics on the long wavelength side of the second band A2 of the optical filter 10 and the cutoff characteristics on the short wavelength side of the third band A3 are substantially similar to the filter characteristics of the third filter 40. That is, on the shorter wavelength side (approximately 864 nm to approximately 900 nm) than 900 nm, the transmittance of the first filter 20 and the second filter 30 is approximately 100% (95% or more). However, the filter characteristics of the third filter 40 are reflected almost as they are. As described above, the transmission characteristics on the long wavelength side of the second band A2 of the optical filter 10 and the cutoff characteristics on the short wavelength side of the third band A3 are formed by the third filter 40.

Further, in the third band A3, a cutoff band is provided in which the transmittance of the optical filter 10 is 5% or less in the wavelength band from the shorter wavelength side than 900 nm to the long wavelength end (1100 nm) of the near infrared light region. It has been. The cut-off band of the third band A3 of the optical filter 10 is substantially similar to the filter characteristics of the third filter 40. That is, in the wavelength band from the shorter wavelength side (approximately 900 nm) than 900 nm to the long wavelength end (1100 nm) in the near-infrared light region, the transmittance of the third filter 40 is approximately 0% (5% or less). Therefore, the filter characteristics of the optical filter 10 reflect the filter characteristics of the third filter 40 substantially as they are. In this way, the third filter 40 forms the cutoff band of the third band A3 of the optical filter 10. In the third band A3 of the optical filter 10, the bandwidth of the cut-off band where the transmittance is 5% or less is approximately 200 nm in this example.

According to the present embodiment, in the first band A1 of the optical filter 10, the bandwidth of the cutoff band where the transmittance is 5% or less is set to at least 100 nm. Can be ensured widely, and the cutoff characteristic of the first band A1 can be sufficiently ensured. Thereby, the transmission of the red component can be sufficiently suppressed, and the occurrence of color mixing due to the transmission of the red component can be suppressed. As a result, it is possible to suppress a decrease in color reproducibility of an image captured by the imaging device. The upper limit value of the bandwidth of the cutoff band of the first band A1 is not particularly limited, and may be, for example, 150 nm or 250 nm.

Here, since the half-value wavelength of the second filter 30 (the wavelength at which the transmittance is 50%) is on the longer wavelength side than the half-value wavelength of the first filter 20, the second filter 30 absorbs the light by the second absorption. The amount of light reflected by the filter 30 is suppressed. Thereby, generation | occurrence | production of the ghost resulting from reflection of the light by the 2nd filter 30 can be suppressed.

In the present embodiment, since the first filter 20 is formed of an infrared absorber (infrared absorbing resin), the optical filter 10 is more visible than when the first filter 20 is formed of a dielectric multilayer film. The incident angle dependency in the light region can be reduced, and the occurrence of ghosts and flares in the image captured by the imaging device can be suppressed. This point will be described with reference to FIG. FIG. 9 is a diagram illustrating a part of each filter characteristic when the light incident angle α (see FIG. 1) is 0 °, 10 °, 20 °, and 30 ° in the optical filter 10. The filter characteristic when the light incident angle α is 0 ° is denoted by L1, the filter characteristic when the light incident angle α is 10 ° is denoted by L2, and the filter property when the light incident angle α is 20 °. L3 indicates the filter characteristic when the light incident angle α is 30 °, and L4.

As shown in FIG. 9, in the near-infrared light region, the waveform of the optical filter 10 shifts to the short wavelength side as the incident angle α of light increases. This is because the filter characteristics of the optical filter 10 are formed by the second and

third filters

30 and 40 made of a dielectric multilayer film in the near-infrared light region. The incident angle dependency of the filter 10 is increased. Therefore, in the near-infrared light region, when it is desired to detect only light of a specific wavelength by the image sensor, the detection efficiency may be deteriorated.

On the other hand, in the visible light region, the shift amount of the waveform of the optical filter 10 to the short wavelength side is smaller than in the near-infrared light region. This is because the filter characteristics of the optical filter 10 are formed by the first filter 20 made of an infrared absorber (infrared absorbing resin) in the visible light region. Thus, in this embodiment, the incident angle dependence in the visible light area | region of the optical filter 10 can be reduced, and it can suppress that a ghost and flare generate | occur | produce in the image imaged with an imaging device. The first filter 20 has almost no incident angle dependency, and even when the light incident angle α is 30 °, the shift amount to the short wavelength side is several nm. That is, the incident angle dependency in the visible light region shown in FIG. 9 is mainly due to the second filter 30, not the first filter 20.

In this embodiment, the filter characteristics of the optical filter 10 are formed by the second and

third filters

30 and 40 in the near-infrared light region. Specifically, the transmission characteristic on the short wavelength side of the second band A2 of the optical filter 10 is formed by the second filter 30, and the transmission characteristic on the long wavelength side of the second band A2 is formed by the third filter 40. Yes. Thereby, in the second band A2 of the optical filter 10, the bandwidth of the transmission band in which the transmittance is 50% or more can be easily changed, and various filter characteristics of the optical filter 10 with respect to the near infrared light region can be changed. Respond flexibly to requests. In the second band A2 of the optical filter 10, the bandwidth of the transmission band where the transmittance is 50% or more is preferably set to 35 nm to 200 nm. In this case, the wavelength band where the transmittance of the second band A2 is 50% is preferably set in the range of 800 nm to 1000 nm. For example, when the bandwidth of the transmission band of the second band A2 is set to 200 nm, the third filter 40 having a filter characteristic that the transmittance rapidly decreases at a wavelength near 1000 nm may be used.

In the present embodiment, the film thickness ratio between the average value of the optical film thickness of the low refractive index film 30L of the second filter 30 and the average value of the optical film thickness of the high refractive index film 30H [of the low refractive index film 30L The average value of the optical film thickness / the average value of the optical film thickness of the high refractive index film 30H] is set to a value within the range of 0.50 to 0.85. Thereby, the bandwidth of the cutoff band having the cutoff characteristic of the second filter 30 can be narrowed, and the transmission band (second band A2) is set in a desired range in the near infrared light region separated from the visible light region. Can be set.

In the present embodiment, the bandwidth of the wavelength at which the transmittance of the first band A1 is 50%, the bandwidth of the wavelength at which the transmittance of the first filter 20 is 50%, and the transmittance of the second filter 30 are as follows. It is larger than the bandwidth of the wavelength of 50%. Accordingly, the first and

second filters

20 and 30 can set the transmission band (second band A2) in a desired range in the near-infrared light region.

The embodiment disclosed herein is illustrative in all respects and does not serve as a basis for limited interpretation. The technical scope of the present invention is not interpreted only by the above-described embodiments, but is defined based on the description of the scope of claims. Further, the technical scope of the present invention includes all modifications within the meaning and scope equivalent to the scope of the claims.

In the above-described embodiment, the optical filter 10 has transmission characteristics in substantially the entire visible light region. However, the present invention is not limited to this, and the optical filter 10 has transmission properties only in a part of the visible light region. It is good also as a structure.

The first filter 20 of the above embodiment is an example, and the wavelength at which the transmittance is 50% in the visible light region is a wavelength in the range of 640 nm to 660 nm, and the absorption maximum is in the range of 650 nm to 800 nm. The first filter 20 may have a configuration other than the above embodiment. For example, in the said embodiment, although the infrared rays absorber which made the transparent resin contain the compound which absorbs infrared rays was used as the 1st filter 20, it is not restricted to this, As 1st filter 20, base materials, such as glass, are used. You may use the infrared absorber of the structure which apply | coated the compound (infrared absorbing ink) which absorbs infrared rays on the surface.

The second filter 30 of the above embodiment is an example, and the wavelength at which the transmittance is 50% is a wavelength in the range of 685 nm to 710 nm, and the cutoff band at which the transmittance is 5% or less is close. As long as it is provided over the range of at least 100 nm in the infrared light region, the second filter 30 may have a configuration other than the above embodiment. For example, the second filter 30 may be configured by combining a plurality of filters (dielectric multilayer films). Similarly, the third filter 40 may be configured by combining a plurality of filters (dielectric multilayer films).

Here, another embodiment (second embodiment) of the optical filter of the present invention will be described with reference to FIGS.

The optical filter 100 shown in FIGS. 10 to 15 is an optical filter provided in the imaging device, and has transmission characteristics in two wavelength bands, a visible light region and a near infrared light region. The wavelength band having the transmission characteristic in the visible light region and the wavelength band having the transmission characteristic in the near infrared light region are provided apart from each other. Specifically, as shown in FIG. 10, the optical filter 100 includes a first filter 120 made of an infrared absorber, and a second filter 130 made of a dielectric multilayer film coated on one surface of the first filter 120. And a third filter 140 made of a dielectric multilayer film coated on the other surface of the first filter 120. The optical filter 100 exhibits filter characteristics (transmittance waveform) as shown in FIG. Hereinafter, each configuration of the optical filter 100 will be described.

-First filter-
In this embodiment, the 1st filter 120 which is an infrared rays absorber becomes the structure by which the infrared rays absorption ink (infrared absorption pigment | dye) 120b which absorbs infrared rays was apply | coated to one side of the transparent base material (transparent substrate) 120a. Yes. The transparent substrate 120a is a colorless and transparent glass substrate. As such a glass substrate, for example, D263Teco (manufactured by Schott), BK7, or the like can be used. As the infrared absorbing dye 120b, for example, squarylium dye, phthalocyanine dye, cyanine dye, or the like can be used. Such an infrared absorbing dye 120b is applied to the surface of the transparent substrate 120a in the state of a coating liquid prepared by mixing with a transparent resin, a solvent, or the like. By using a glass substrate as the transparent base material 120a, the rigidity of the first filter 120 can be improved, and the first filter 120 of the second and

third filters

130 and 140, which will be described later, is caused by stress during film formation. Distortion can be suppressed. However, the transparent substrate 120a may be other than glass as long as it is a colorless and transparent substrate. For example, the transparent substrate 120a may be a transparent resin such as polyethylene terephthalate, polycarbonate, and cycloolefin polymer.

The manufacture of the first filter 120 having the above configuration is performed by the following procedure, for example.

First, the infrared absorbing dye 120b is mixed with a transparent resin, a solvent, and the like to prepare a coating liquid for the infrared absorbing dye 120b (coating liquid preparing step). As an example, a solution in which polymethyl methacrylate as a solvent is mixed in a ratio of 5 to 15% by weight with methyl ethyl ketone as a transparent resin to prepare a solution in which polymethyl methacrylate is dissolved. To this solution, a cyanine infrared absorbing dye as the infrared absorbing dye 120b is added at a ratio of 0.1 to 1.0% by weight to prepare a coating liquid for the infrared absorbing dye 120b. As the transparent resin, for example, acrylic, epoxy, polystyrene, polyester, cyclic olefin, or the like can be used. As the solvent, for example, ketone (methyl ethyl ketone, etc.), hydrocarbon (toluene, etc.), ester (methyl acetate, etc.), ether (tetrahydrofuran, etc.), alcohol (ethanol, etc.) can be used. is there. Moreover, you may add polymerization initiators, such as a photoinitiator and a thermal polymerization initiator, as needed. In addition, you may purchase the infrared rays absorption pigment | dye 120b (for example, epoxy resin coating material) marketed in the state of a paint, and may apply | coat the infrared rays absorption pigment | dye 120b to the transparent base material 120a. In this case, a coating liquid preparation process Can be omitted.

Next, the infrared absorbing dye 120b coating liquid prepared in the coating liquid preparation process is uniformly applied to the surface of the transparent substrate 120a with a predetermined thickness (application process). In this coating step, the coating liquid is applied using, for example, a spin coater, a die coater, a bar coater, or the like.

Next, the transparent base material 120a coated with the coating liquid in the coating step is dried, the solvent contained in the coating liquid is volatilized, and the transparent resin contained in the coating liquid is cured (drying). Process). In this drying step, for example, the solvent is volatilized and the transparent resin is cured by heating at about 100 ° C. for about 5 minutes using an oven, a hot plate, or the like. When a photopolymerization initiator is added, the transparent resin is cured using photopolymerization.

As shown in FIG. 12, the first filter 120 has an absorption maximum near the boundary between the visible light region and the near-infrared light region, and the transmittance of the first filter 120 is minimized. FIG. 12 shows the filter characteristics of the first filter 120 when the incident angle α of light (see FIG. 1) is 0 ° (in the case of vertical incidence).

Specifically, the first filter 120 has transmission characteristics in substantially the entire visible light region (400 nm to 700 nm), and gently transmits on the long wavelength side (longer wavelength side than 600 nm) of the visible light region. It has a transmission characteristic with a decreasing rate. In the visible light region, the range where the transmittance of the first filter 120 is 50% or more is the wavelength band from the short wavelength end (400 nm) of the visible light region to approximately 654 nm. The range in which the transmittance of the first filter 120 is 80% or more is the wavelength band from the short wavelength end (400 nm) of the visible light region to approximately 606 nm. The range in which the transmittance of the first filter 120 is 90% or more is a wavelength band of approximately 584 nm from the short wavelength end (400 nm) in the visible light region. A range where the transmittance of the first filter 120 is 95% or more is a wavelength band of about 434 nm to about 564 nm.

The first filter 120 has a transmission characteristic in substantially the entire region of the near infrared light region (700 nm to 1100 nm), and the transmittance on the short wavelength side (shorter wavelength side than 750 nm) of the near infrared light region. Has increased transmission characteristics. In the near infrared light region, the range in which the transmittance of the first filter 120 is 50% or more is a wavelength band from approximately 796 nm to the long wavelength end (1100 nm) of the near infrared light region. The range in which the transmittance of the first filter 120 is 80% or more is the wavelength band from approximately 814 nm to the long wavelength end (1100 nm) in the near infrared light region. The range in which the transmittance of the first filter 120 is 90% or more is the wavelength band from approximately 826 nm to the long wavelength end (1100 nm) in the near infrared light region. The range in which the transmittance of the first filter 120 is 95% or more is the wavelength band from approximately 838 nm to the long wavelength end (1100 nm) of the near infrared light region. On the short wavelength side in the near-infrared light region, the change rate (increase rate) of the transmittance of the first filter 120 is larger than the change rate (decrease rate) on the long wavelength side in the visible light region.

On the other hand, the absorption characteristics of the first filter 120 near the boundary between the visible light region and the near-infrared light region are as follows. The range in which the transmittance of the first filter 120 is 20% or less is a wavelength band of approximately 722 nm to approximately 778 nm. The range in which the transmittance of the first filter 120 is 10% or less is a wavelength band of approximately 742 nm to approximately 762 nm. The transmittance of the first filter 120 is a minimum value (approximately 8.6%) at a wavelength of approximately 752 nm (absorption maximum). In the present embodiment, the absorption maximum of the first filter 120 exists at a wavelength of approximately 752 nm, but the absorption maximum of the first filter 120 is within the range of 650 nm to 800 nm. Good.

-Second filter-
As shown in FIG. 10, the second filter 130 is configured by a dielectric multilayer film formed on one surface 120 A of the first filter 120. In the present embodiment, the second filter 130 is formed on the surface of the first filter 120 that is not provided with the infrared absorbing dye 120b described above. That is, the second filter 130 is provided on the surface of the transparent substrate 120 a of the first filter 120.

The second filter 130, a TiO ₂ is a high-refractive-index film 130H, has a structure in which the SiO ₂ which is a low refractive index film 130L are alternately stacked. In the present embodiment, the second filter 130 has a configuration in which the second filter 30 and the third filter 40 of the optical filter 10 of the first embodiment described above are formed as one filter. That is, the second filter 130 is configured by combining a plurality of filters. Specifically, a dielectric multilayer film having substantially the same configuration as that of the second filter 30 (see FIG. 5) of the optical filter 10 of the first embodiment is formed on one surface 120A of the first filter 120. A dielectric multilayer film having substantially the same configuration as that of the third filter 40 (see FIG. 7) of the optical filter 10 of the first embodiment is further formed on the multilayer film.

In the

second filter

130, 27 layers of the high-refractive index film 130H are formed and 28 layers of the low-refractive index film 130L are formed, for a total of 55 layers. The odd-numbered layers counted from the first filter 120 side are the low-refractive index films 130L, and the even-numbered layers are the high-refractive index films 130H. The first layer (lowermost layer) on the first filter 120 side is the low refractive index film 130L, and the 55th layer (uppermost layer) on the most atmospheric side is also the low refractive index film 130L. Note that the stacking order of the high refractive index film 130H and the low refractive index film 130L is not limited to this example, and the odd-numbered layer counted from the first filter 120 side is the high-refractive index film 130H, and the even-numbered layer is low. The refractive index film 130L may be used. The number of layers of the high refractive index film 130H and the low refractive index film 130L may be the same.

In the present embodiment, the high refractive index film 130H is made of TiO ₂ , but is not limited thereto, and may be a material such as ZrO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , for example. That is, the material of the high refractive index film 130H is preferably a material having a refractive index larger than 2.0. Further, the low refractive index film 130L is not limited to SiO ₂ but may be a material such as MgF ₂ . That is, the material of the low refractive index film 130L is preferably a material having a refractive index smaller than that of the high refractive index film 130H, and more preferably a material having a refractive index smaller than 1.5.

Each layer (the low refractive index film 130L and the high refractive index film 130H) of the second filter 130 is a surface of the both surfaces of the first filter 120 on which the infrared absorbing dye 120b is not provided by a known vacuum deposition apparatus. Alternately vacuum deposition. The vapor deposition film thickness is designed based on the optical film thickness that is the product of the refractive index and the physical film thickness. Since the configuration of each layer of the second filter 130 is substantially the same as the configuration of each layer of the second and

third filters

30 and 40 of the optical filter 10 of the first embodiment (see FIGS. 5 and 7), it will be described here. Is omitted. In the second filter 130, as in the optical filter 10 of the first embodiment, the average optical film thickness of the low refractive index film 130L is smaller than the average optical film thickness of the high refractive index film 130H. The film thickness ratio between the average value of the optical thickness of the low refractive index film 130L and the average value of the optical thickness of the high refractive index film 130H [average value of optical thickness of the low refractive index film 130L / high refractive index The average value of the optical film thickness of the film 130H] is preferably 0.50 to 0.85.

As shown in FIG. 13, the second filter 130 has a transmission characteristic in substantially the entire visible light region (400 nm to 700 nm) and a transmission characteristic in a part of the near infrared light region (700 nm to 1100 nm). FIG. 13 shows the filter characteristics of the second filter 130 when the light incident angle α (see FIG. 1) is 0 ° (in the case of vertical incidence).

Specifically, the second filter 130 has a transmission characteristic in substantially the entire visible light region (400 nm to 700 nm), and rapidly transmits on the long wavelength side (longer wavelength side than 680 nm) of the visible light region. It has a transmission characteristic with a decreasing rate. In the visible light region, the range in which the transmittance of the second filter 130 is 50% or more is a wavelength band from approximately 406 nm to approximately 694 nm. The range in which the transmittance of the second filter 130 is 80% or more is a wavelength band from approximately 408 nm to approximately 690 nm. The range in which the transmittance of the second filter 130 is 90% or more is a wavelength band of about 408 nm to about 688 nm. The range where the transmittance of the second filter 130 is 95% or more is the wavelength band of about 410 nm to about 686 nm.

The second filter 130 has transmission characteristics in a part of the near infrared light region (700 nm to 1100 nm). The wavelength band having the transmission characteristics in the near-infrared light region of the second filter 130 is provided apart from the wavelength band having the transmission characteristics in the visible light region. Specifically, the second filter 130 has a transmission characteristic in a part of the wavelength band of 800 nm to 950 nm, and the transmittance rapidly increases on the longer wavelength side than 800 nm in the near infrared light region. It has a transmission characteristic in which the transmittance sharply decreases on the shorter wavelength side than 950 nm. In the near-infrared light region, the range in which the transmittance of the second filter 130 is 50% or more is a wavelength band of approximately 830 nm to approximately 876 nm. A range where the transmittance of the second filter 130 is 80% or more is a wavelength band of about 836 nm to about 868 nm. The range where the transmittance of the second filter 130 is 90% or more is the wavelength band of about 838 nm to about 866 nm. The range in which the transmittance of the second filter 130 is 95% or more is a wavelength band of about 840 nm to about 862 nm.

On the other hand, the cutoff characteristic of the second filter 130 in the vicinity of the boundary between the visible light region and the near infrared light region is as follows. The range in which the transmittance of the second filter 130 is 20% or less is a wavelength band of about 700 nm to about 824 nm. A range where the transmittance of the second filter 130 is 10% or less is a wavelength band of about 706 nm to about 818 nm. The range in which the transmittance of the second filter 130 is 5% or less is a wavelength band of approximately 712 nm to approximately 812 nm.

-Third filter-
As shown in FIG. 10, the third filter 140 is composed of a dielectric multilayer film formed on the other surface 120 B of the first filter 120. In the present embodiment, the third filter 140 is formed on the surface of the first filter 120 on which the infrared absorbing dye 120b described above is provided. That is, the third filter 140 is provided on the surface of the infrared absorbing dye 120b of the first filter 120.

In the present embodiment, the third filter 140 is configured as an antireflection film having filter characteristics as shown in FIG. Specifically, as shown in FIG. 14, the third filter 140 has a configuration in which TiO _{2 that} is the high refractive index film 140H and SiO ₂ that is the low refractive index film 140L are alternately stacked. . Four high refractive index films 140H are formed, and five low refractive index films 140L are formed, for a total of nine layers. The odd-numbered layers counted from the first filter 120 side are the low-refractive index films 140L, and the even-numbered layers are the high-refractive index films 140H. The first layer (lowermost layer) closest to the first filter 120 is the low refractive index film 140L, and the ninth layer (uppermost layer) closest to the atmosphere is also the low refractive index film 140L. The order in which the high refractive index film 140H and the low refractive index film 140L are stacked is not limited to this example, and the odd-numbered layer counted from the first filter 120 side is the high-refractive index film 140H, and the even-numbered layer is low. The refractive index film 140L may be used. The number of layers of the high refractive index film 140H and the low refractive index film 140L may be the same.

In the present embodiment, the high refractive index film 140H is made of TiO ₂ , but is not limited thereto, and may be a material such as ZrO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , for example. That is, the material of the high refractive index film 140H is preferably a material having a refractive index larger than 2.0. Further, the low refractive index film 140L is not limited to SiO ₂ but may be a material such as MgF ₂ . That is, the material of the low refractive index film 140L is preferably a material having a refractive index smaller than that of the high refractive index film 140H, and more preferably a material having a refractive index smaller than 1.5.

Each layer (the low refractive index film 140L and the high refractive index film 140H) of the third filter 140 is a surface on which the infrared absorbing dye 120b is provided among both surfaces of the first filter 120 by a known vacuum deposition apparatus. Alternately vacuum deposition. The vapor deposition film thickness is designed based on the optical film thickness that is the product of the refractive index and the physical film thickness, and the optical film thickness of the third filter 140 is designed, for example, as shown in FIG. The center wavelength (510 nm) in FIG. 14 is the center wavelength in the film thickness design.

As shown in FIG. 15, the third filter 140 has transmission characteristics in substantially the entire visible light region (400 nm to 700 nm) and substantially the entire near infrared light region (700 nm to 1100 nm). FIG. 15 shows the filter characteristics of the third filter 140 when the incident angle α of light (see FIG. 1) is 0 ° (in the case of vertical incidence). Specifically, in the third filter 140, the transmittance of the third filter 140 is 95% or more in substantially the entire visible light region. In the near-infrared light region, the third filter 140 has a transmittance of 95% or more from the short wavelength end (700 nm) of the near-infrared light region to the shorter wavelength side than 900 nm. In this case, the transmittance of the third filter 140 is 95% at a wavelength of approximately 1012 nm, and the transmittance of the third filter 140 is 90.4% at the long wavelength end (1100 nm) in the near-infrared light region. It has become.

-Optical filter characteristics-
The filter characteristics of the first to

third filters

120, 130, and 140 of this embodiment are as shown in FIGS. 12, 13, and 15, respectively. The filter characteristics of the entire optical filter 100 are obtained by integrating the filter characteristics of the first filter 120, the filter characteristics of the second filter 130, and the filter characteristics of the third filter 140 (see FIG. 11). That is, the transmittance waveform of the first filter 120 (see FIG. 12), the transmittance waveform of the second filter 130 (see FIG. 13), and the transmittance waveform of the third filter 140 (see FIG. 15) overlap. A transmittance waveform of the optical filter 100 shown in FIG. 11 is obtained. That is, according to the optical filter 100 of the present embodiment, as shown in FIG. 11, filter characteristics having transmission characteristics in two wavelength bands of the visible light region and the near infrared light region can be obtained. The wavelength band having transmission characteristics in the near-infrared light region of the optical filter 100 is provided apart from the wavelength band having transmission properties in the visible light region.

Specifically, as shown in FIG. 11, the optical filter 100 has transmission characteristics in substantially the entire visible light region (400 nm to 700 nm), and has a longer wavelength side (wavelength longer than 600 nm) in the visible light region. Side), the transmittance gradually decreases. Such characteristics of the optical filter 100 in the visible light region are mainly obtained by the first filter 120. The waveform in which the transmittance of the optical filter 100 decreases on the long wavelength side of the visible light region (longer wavelength side than 600 nm) is substantially similar to the waveform in which the transmittance of the first filter 120 decreases. That is, in the region on the long wavelength side of the visible light region, the transmittance of the second filter 130 and the third filter 140 is approximately 100% (95% or more). The filter characteristics of the filter 120 are reflected as they are.

More specifically, in the visible light region, the range in which the transmittance of the optical filter 100 is 50% or more is a wavelength band from the short wavelength end (400 nm) of the visible light region to approximately 650 nm. A range where the transmittance of the optical filter 100 is 80% or more is a wavelength band of about 408 nm to about 602 nm. A range where the transmittance of the optical filter 100 is 90% or more is a wavelength band of about 424 nm to about 576 nm. A range where the transmittance of the optical filter 100 is 95% or more is a wavelength band of about 454 nm to about 540 nm.

Further, as shown in FIG. 11, the optical filter 100 has transmission characteristics in a part of the near-infrared light region. That is, the optical filter 100 is cut off in the first band A11 provided from the long wavelength side of the visible light region to the near infrared light region and the third band A13 provided on the longer wavelength side than the first band A11. In addition to having a characteristic, the second band A12 provided between the first band A11 and the third band A13 has a transmission characteristic.

The first band A11 is provided from a longer wavelength side than 640 nm to a longer wavelength side than 800 nm, and a cutoff band having a transmittance of 5% or less is provided in the first band A11. The third band A13 is provided from the shorter wavelength side than 900 nm to the long wavelength end (1100 nm) in the near-infrared light region, and the third band A13 has a cutoff band in which the transmittance is 5% or less. Is provided. The transmission band of the second band A12 is formed by the cutoff band of the first band A11 and the cutoff band of the third band A13. In the second band A12, the transmittance of the optical filter 100 is 50% at a wavelength longer than 800 nm (approximately 832 nm) and at a wavelength shorter than 900 nm (approximately 874 nm).

Specifically, as shown in FIG. 11, the wavelength band in which the transmittance of the first band A11 is 50% is a wavelength band of about 650 nm to about 832 nm. The wavelength band where the transmittance of the second band A12 is 50% is a wavelength band of about 832 nm to about 874 nm. The wavelength band in which the transmittance of the third band A13 is 50% is a wavelength band from approximately 874 nm to the long wavelength end (1100 nm) of the near infrared light region.

The cutoff characteristic in the first band A11 of the optical filter 100 is as follows. A range where the transmittance of the optical filter 100 is 20% or less is a wavelength band of about 690 nm to about 824 nm. The range in which the transmittance of the optical filter 100 is 10% or less is a wavelength band of approximately 696 nm to approximately 820 nm. The range in which the transmittance of the optical filter 100 is 5% or less is a wavelength band of about 700 nm to about 814 nm. As described above, the optical filter 100 has a characteristic that in the first band A11, the transmittance is rapidly increased on the longer wavelength side than 800 nm in the near-infrared light region.

Moreover, the cutoff characteristic in the third band A13 of the optical filter 100 is as follows. The range in which the transmittance of the optical filter 100 is 20% or less is a wavelength band from approximately 884 nm to the long wavelength end (1100 nm) of the near infrared light region. The range in which the transmittance of the optical filter 100 is 10% or less is the wavelength band from approximately 890 nm to the long wavelength end (1100 nm) of the near infrared light region. The range in which the transmittance of the optical filter 100 is 5% or less is the wavelength band from approximately 898 nm to the long wavelength end (1100 nm) of the near infrared light region. As described above, the optical filter 100 has a characteristic that the transmittance is rapidly reduced in the third band A13 on the shorter wavelength side than 900 nm in the near-infrared light region.

On the other hand, the transmission characteristics in the second band A12 of the optical filter 100 are as follows. A range where the transmittance of the optical filter 100 is 50% or more is a wavelength band of about 832 nm to about 874 nm. A range where the transmittance of the optical filter 100 is 80% or more is a wavelength band of about 836 nm to about 868 nm. The range in which the transmittance of the optical filter 100 is 90% or more is a wavelength band of approximately 840 nm to approximately 864 nm. Thus, in the second band A12, the optical filter 100 has a characteristic that the transmittance sharply increases on the longer wavelength side than 800 nm in the near infrared light region, and more than 900 nm in the near infrared light region. Also has a characteristic that the transmittance decreases rapidly on the short wavelength side.

In the present embodiment, the cutoff characteristic on the short wavelength side of the first band A11 of the optical filter 100 is formed by the first filter 120 and the second filter 130. Further, the cutoff characteristic on the long wavelength side of the first band A11 of the optical filter 100 and the transmission characteristic on the short wavelength side of the second band A12 are formed by the second filter 130. Further, the transmission characteristics on the long wavelength side of the second band A12 of the optical filter 100 and the cutoff characteristics on the short wavelength side of the third band A13 are formed by the second filter 130. In the first band A11 of the optical filter 100, the bandwidth of the cutoff band where the transmittance is 5% or less is at least 100 nm. This point will be described below.

As shown in FIG. 11, in the first band A11, in the near-infrared light region, the optical filter 100 has a wavelength band from the short wavelength end (700 nm) of the near-infrared light region to the longer wavelength side than 800 nm. A cut-off band in which the transmittance is 5% or less is provided. The cutoff band of the first band A11 is provided in a range of approximately 700 nm to approximately 814 nm.

The cut-off band of the first band A11 of the optical filter 100 is formed by the first filter 120 and the second filter 130. That is, in the near-infrared light region, in the wavelength band from the short wavelength end (700 nm) of the near-infrared light region to the short wavelength side (approximately 712 nm) of the near-infrared light region, the cutoff band of the first band A11 is The filter characteristics of the first filter 120 and the filter characteristics of the second filter 130 are combined. On the other hand, in the wavelength band from the short wavelength side (approximately 712 nm) in the near-infrared light region to the longer wavelength side (approximately 814 nm) than 800 nm, the cutoff band of the first band A11 is the filter characteristic of the second filter 130. It has been imitated. That is, in the wavelength band from the short wavelength side (approximately 712 nm) in the near infrared light region to the longer wavelength side (approximately 814 nm) than 800 nm, the transmittance of the second filter 130 is approximately 0% (5% or less). Therefore, the filter characteristics of the optical filter 100 reflect the filter characteristics of the second filter 130 substantially as they are.

Thus, the cut-off band of the first band A11 of the optical filter 100 is formed by the first filter 120 and the second filter 130. In the first band A11 of the optical filter 100, in the near infrared light region, the bandwidth of the cutoff band where the transmittance is 5% or less is set to at least 100 nm, and in this example, is approximately 112 nm. .

Next, the optical filter 100 has a filter characteristic in which the transmittance rapidly increases near the boundary between the first band A11 and the second band A12 on the longer wavelength side than 800 nm in the near-infrared light region. In the range of approximately 814 nm to approximately 840 nm, the transmittance of the optical filter 100 increases from 5% to 90%. The cut-off characteristics on the long wavelength side of the first band A11 and the transmission characteristics on the short wavelength side of the second band A12 of the optical filter 100 are substantially similar to the filter characteristics of the second filter 130. That is, the transmittance of the first filter 120 and the third filter 140 is approximately 100% (95% or more) on the longer wavelength side (approximately 814 nm to approximately 840 nm) than 800 nm in the near infrared light region. The filter characteristics of the optical filter 100 reflect the filter characteristics of the second filter 130 as they are. As described above, the second filter 130 forms the cutoff characteristic on the long wavelength side of the first band A11 of the optical filter 100 and the transmission characteristic on the short wavelength side of the second band A12.

Next, in the second band A12, the transmittance of the optical filter 100 in the wavelength band from the longer wavelength side than 800 nm to the shorter wavelength side than 900 nm, specifically, in the wavelength band of about 840 nm to about 864 nm. A transmission band of 90% or more is provided. The transmission band of the second band A12 of the optical filter 100 is substantially similar to the filter characteristics of the second filter 130. That is, in the wavelength band of approximately 840 nm to approximately 864 nm, the transmittance of the first filter 120 and the third filter 140 is approximately 100% (95% or more), so that the filter characteristics of the optical filter 100 are the second filter. The filter characteristics of 130 are reflected as they are. Thus, the transmission band of the second band A12 of the optical filter 100 is formed by the second filter 130. In the second band A12 of the optical filter 100, the bandwidth of the transmission band where the transmittance is 90% or more is approximately 24 nm in this example. In the second band A12 of the optical filter 100, the bandwidth of the transmission band where the transmittance is 50% or more is approximately 42 nm in this example.

Next, the optical filter 100 has a filter characteristic in which the transmittance rapidly decreases near the boundary between the second band A12 and the third band A13 on the shorter wavelength side than 900 nm in the near-infrared light region. In the range from about 864 nm to about 898 nm, the transmittance of the optical filter 100 decreases from 90% to 5%. The transmission characteristics on the long wavelength side of the second band A12 of the optical filter 100 and the cutoff characteristics on the short wavelength side of the third band A13 are substantially similar to the filter characteristics of the second filter 130. That is, on the shorter wavelength side (approximately 864 nm to approximately 898 nm) than 900 nm, the transmittance of the first filter 120 and the third filter 140 is approximately 100% (95% or more). However, the filter characteristics of the second filter 130 are reflected almost as they are. As described above, the second filter 130 forms the transmission characteristic on the long wavelength side of the second band A12 of the optical filter 100 and the cutoff characteristic on the short wavelength side of the third band A13.

Further, in the third band A13, a cutoff band is provided in which the transmittance of the optical filter 100 is 5% or less in the wavelength band from the shorter wavelength side than 900 nm to the long wavelength end (1100 nm) in the near infrared light region. It has been. The cut-off band of the third band A13 of the optical filter 100 is substantially similar to the filter characteristics of the second filter 130. That is, in the wavelength band from the shorter wavelength side than 900 nm (approximately 898 nm) to the long wavelength end (1100 nm) of the near infrared light region, the transmittance of the second filter 130 is approximately 0% (5% or less). Therefore, the filter characteristics of the optical filter 100 reflect the filter characteristics of the second filter 130 almost as they are. Thus, the cutoff band of the third band A13 of the optical filter 100 is formed by the second filter 130. In the third band A13 of the optical filter 100, the bandwidth of the cut-off band where the transmittance is 5% or less is approximately 202 nm in this example.

According to the present embodiment, as in the first embodiment described above, in the first band A11 of the optical filter 100, the bandwidth of the cutoff band where the transmittance is 5% or less is set to at least 100 nm. The bandwidth of the cut-off band can be ensured wider than before, and the cut-off characteristics of the first band A11 can be sufficiently secured. Thereby, the transmission of the red component can be sufficiently suppressed, and the occurrence of color mixing due to the transmission of the red component can be suppressed. As a result, it is possible to suppress a decrease in color reproducibility of an image captured by the imaging device. The upper limit value of the bandwidth of the cutoff band of the first band A11 is not particularly limited, and may be, for example, 150 nm or 250 nm.

Here, since the half-value wavelength of the second filter 130 (the wavelength at which the transmittance is 50%) is on the longer wavelength side than the half-value wavelength of the first filter 120, the second filter 130 absorbs light by the second filter 130. The amount of light reflected by the filter 130 is suppressed. Thereby, generation | occurrence | production of the ghost resulting from reflection of the light by the 2nd filter 130 can be suppressed.

In the present embodiment, as in the first embodiment described above, the first filter 120 is formed of an infrared absorber (transparent substrate and infrared absorbing dye), and therefore the first filter 120 is formed of a dielectric multilayer film. Compared to the case where the optical filter 100 is formed, the incident angle dependency in the visible light region of the optical filter 100 can be reduced (see FIG. 9), and the occurrence of ghosts and flares in the image captured by the imaging device is also suppressed. it can.

In addition, in this embodiment, the filter characteristics of the optical filter 100 are formed by the second filter 130 in the near-infrared light region. Specifically, the transmission characteristics on the short wavelength side of the second band A12 of the optical filter 100 and the transmission characteristics on the long wavelength side of the second band A12 are formed by the second filter 130. Thereby, in the second band A12 of the optical filter 100, the bandwidth of the transmission band where the transmittance is 50% or more can be easily changed. Respond flexibly to requests. In the second band A12 of the optical filter 100, the bandwidth of the transmission band where the transmittance is 50% or more is preferably set to 35 nm to 200 nm. In this case, the wavelength band where the transmittance of the second band A12 is 50% is preferably set in the range of 800 nm to 1000 nm. For example, when the bandwidth of the transmission band of the second band A12 is set to 200 nm, the second filter 130 may be configured so that the transmittance is rapidly reduced at a wavelength near 1000 nm. Thus, since the second filter 130 capable of forming the transmission characteristics of the second band A12 with a single filter can be formed on the surface opposite to the surface on which the infrared absorbing dye 120b is formed, Damage to the infrared absorbing dye 120b (particularly damage due to heat) can be suppressed.

Further, in the present embodiment, as in the first embodiment described above, the film of the average value of the optical film thickness of the low refractive index film 130L of the second filter 130 and the average value of the optical film thickness of the high refractive index film 130H. The thickness ratio [average optical film thickness of low refractive index film 130L / average optical film thickness of high refractive index film 130H] is set to a value in the range of 0.50 to 0.85. Thereby, the bandwidth of the cutoff band having the cutoff characteristic of the second filter 130 can be narrowed, and the transmission band (second band A12) is set in a desired range in the near infrared light region separated from the visible light region. Can be set.

Further, in the present embodiment, as in the first embodiment described above, the bandwidth of the wavelength at which the transmittance of the first band A11 is 50% is the bandwidth of the wavelength at which the transmittance of the first filter 120 is 50%. And the transmittance of the second filter 130 is larger than the bandwidth of the wavelength at which the transmittance is 50%. As a result, the first and

second filters

120 and 130 can set the transmission band (second band A12) in a desired range in the near-infrared light region.

In the present embodiment, the first filter 120 has a configuration in which the infrared absorbing dye 120b is applied to the transparent substrate 120a. Therefore, by adjusting the type, concentration, thickness, and the like of the infrared absorbing dye 120b, The desired infrared absorption characteristics can be easily obtained as compared with the case where an absorbing resin substrate is used.

Although the cutoff characteristic on the short wavelength side of the first band A11 is formed by the first filter 120 and the second filter 130, the cutoff characteristic on the short wavelength side of the first band A11 is not limited to this. You may form only by 120.

In the above, the second filter 130 is formed on the surface of the first filter 120 where the infrared absorbing dye 120b is not provided, and the second filter 130 is formed on the surface where the infrared absorbing dye 120b is provided. Three filters 140 were formed. However, the present invention is not limited to this. Of the two surfaces of the first filter 120, the second filter 130 is formed on the surface on which the infrared absorbing dye 120 b is provided, and the surface on which the infrared absorbing dye 120 b is not provided. Alternatively, the third filter 140 may be formed.

This application claims priority based on Japanese Patent Application No. 2016-169785 filed in Japan on August 31, 2016. By this reference, the entire contents thereof are incorporated into the present application.

The present invention is an optical filter provided in an imaging device, and can be used for an optical filter having transmission characteristics in two wavelength bands of a visible light region and a near infrared light region.

10,100 Optical filter 20,120 First filter 30,130 Second filter 40,140 Third filter A1, A11 First band A2, A12 Second band A3, A13 Third band

Claims

An optical filter having transmission characteristics in two wavelength bands of a visible light region and a near infrared light region,
A second filter made of a dielectric multilayer film is formed on one surface of the first filter made of an infrared absorber, and a third filter made of a dielectric multilayer film is formed on the other surface of the first filter;
The first band provided from the long wavelength side of the visible light region to the near infrared light region, and the third band provided on the longer wavelength side than the first band have a cutoff characteristic, and the first band and Having a transmission characteristic in a second band provided between the third bands;
In the first band, an optical filter is characterized in that a bandwidth of a cut-off band where a transmittance is 5% or less is set to at least 100 nm.
The optical filter according to claim 1,
In the first filter, the wavelength at which the transmittance is 50% in the visible light region is a wavelength in the range of 640 nm to 660 nm, and has an absorption maximum in the range of 650 nm to 800 nm.
In the second filter, the wavelength at which the transmittance is 50% is a wavelength in the range of 685 nm to 710 nm, and the cutoff band where the transmittance is 5% or less is at least 100 nm in the near-infrared light region. An optical filter provided over a range.
The optical filter according to claim 1 or 2,
An optical filter characterized in that the wavelength at which the transmittance of the second filter is 50% is longer than the wavelength at which the transmittance is 50% in the visible light region of the first filter.
The optical filter according to any one of claims 1 to 3,
The first band is formed by the first filter and the second filter;
The optical filter, wherein the third band is formed by the third filter.
The optical filter according to any one of claims 1 to 4,
The cutoff characteristic on the short wavelength side of the first band is formed by the first filter,
Transmission characteristics on the short wavelength side of the second band are formed by the second filter,
An optical filter characterized in that transmission characteristics on the long wavelength side of the second band are formed by the third filter.
The optical filter according to any one of claims 1 to 3,
The first filter has a configuration in which an infrared absorbing dye is applied to a transparent substrate,
The optical filter, wherein the third filter is formed of an antireflection film.
The optical filter according to claim 6,
The first band is formed by the first filter and the second filter;
The optical filter, wherein the third band is formed by the second filter.
The optical filter according to claim 6 or 7,
The cutoff characteristic on the short wavelength side of the first band is formed only by the first filter or by the first filter and the second filter,
The optical filter, wherein the transmission characteristics on the short wavelength side of the second band and the transmission characteristics on the long wavelength side of the second band are formed by the second filter.
The optical filter according to any one of claims 1 to 8,
In the second band, an optical filter characterized in that the bandwidth of the transmission band where the transmittance is 50% is set to 35 nm to 200 nm.
The optical filter according to claim 9,
An optical filter, wherein a transmission band in which the transmittance of the second band is 50% is provided in a range of 800 nm to 1000 nm.
The optical filter according to any one of claims 1 to 10,
The wavelength bandwidth at which the transmittance of the first band is 50%, the bandwidth of the wavelength at which the transmittance of the first filter is 50%, and the wavelength band at which the transmittance of the second filter is 50%. An optical filter characterized by being larger than the width.
The optical filter according to any one of claims 1 to 11,
The second filter has a configuration in which a plurality of filters are combined.
The optical filter according to any one of claims 1 to 12,
The second filter has a configuration in which a plurality of high refractive index films and a plurality of low refractive index films having a refractive index smaller than that of the high refractive index film are alternately stacked.
In the second filter, the average value of the optical thickness of the low refractive index film is smaller than the average value of the optical thickness of the high refractive index film, and the average value of the optical thickness of the low refractive index film, An optical filter characterized in that a film thickness ratio of the high refractive index film to the average value of the optical film thickness is 0.50 to 0.85.